Ok, Here we go.

[Gunther1000]

Has ANYONE ran a 120/60 and a 120/70 back to back and if so could you tell me your impression as to turn in and grip at lean angle. Maybe even bump absorbtion as well? I'm thinking of making a change but fear the loss of side grip as it is 3mm less on the stat sheet.

[the chi]

Maybe this might help a little...see bold...


http://www.superbikeplanet.com/2007/Jun/e/n070611c.htm

The hot race tire diameter is something that changes every few years. Bigger or smaller, some company's engineers will find a breakthrough and all the others will follow. Michelin has introduced a 16-inch front tire for this MotoGP season and the others are now doing the same.

At today's MotoGP post-race test in Catalunya, Bridgestone will test a 16-inch front. Dunlop brought out theirs a few races back.

Michelin says their contact patch on the sixteen stays the same size all the way to full lean. Michelin also says the new tire on the different rim is five percent lighter. That is ultra-important since the 800cc MotoGP era is about corner speed and pushing the front, where the 990cc era was more about getting the massive power to the ground.

[jeeps84]

It depends on rim with. The shorter tires turn in slower and harder to pick up coming out of the corners.

[Gunther1000]

Sorry Rae, I'm talking about stock size 17" rims here.

I hear the 120/60 may turn in less due to the reduced (A) shape and more of a U, but I'm not sure on that one. Also the main concern is the less side grip? If there is any noticable difference in a 70 and 60 let me know.

Rear being a 190/55 vs stock's 190/50. If you notice here im going for more turn in not less. I'm thinking the rear will be enough but shit the 60 front might be win win if its not a huge traction problem.

[jeeps84]

IMO It flat'ns out the tire to much.

[smileyman]

My experience with the fronts is that the 60 is shorter and steepens the front end, speeding up turn in with less stability...Going to the 120/70 front raised the front and provided a slower turn but more stability.

My SV race bike came with the 60 series front and when I swapped to a 70 I raised the rear by almost a half inch to get it in the sweet spot. My ZX636 came with a 120/65 front and likewise when I switched to the 70 I had to raise the forks a little to get it back turning in sweetly...

[No Worries]

Originally Posted by smileyman

My experience with the fronts is that the 60 is shorter and steepens the front end, speeding up turn in with less stability...Going to the 120/70 front raised the front and provided a slower turn but more stability.

My SV race bike came with the 60 series front and when I swapped to a 70 I raised the rear by almost a half inch to get it in the sweet spot. My ZX636 came with a 120/65 front and likewise when I switched to the 70 I had to raise the forks a little to get it back turning in sweetly...

I agree. Putting the smaller-diameter 60 tire on the bike is almost the same as raising the forks above the triple clamp. Tightens the rake of the fork and quickens the steering, but stability is lessened.

[Gunther1000]

I hear you both and while I do know the effect it will have I don't have any ride experiance with a 60. So would anyone be able to tell me if they noticed any shortage of side wall traction in the 60 vs the 70? Thats my only question really...

[DLIT]

If it helps, I started on a '04 R6 and they came with a 60 series. My '06 had a 70 in it. The 60 turns in faster, but it's not as smooth as the 70 throughout the whole corner. That doesn't means it's bad, but after riding on both, I prefer the 70 over the 60. And I don't remember any shortage of sidewall traction. I had no chicken strips on my front of the '04 before I traded it in. I was running Pilot Powers. Tire make will make a difference. Not sure how big of a difference, but there will be one.

[smileyman]

I had no issues with outright traction on either. And that was at the race track. I mean either your in hot and the front pushes or it doesn't eh? I did notice the feel of the 70 being better on turn in due to the different profile. It was tippy even with the suspension adjusted. By that I mean countersteering it onto its side felt somehow better than the 60. More aggressive or confident. Perhaps it was just a placebo effect that gave me more confidence knowing there was extra traction there if I needed it.

This despite most of my front end slide experience came on worn 70 series tires. I did have more laps on the 70 than the 60 so there were more opportunities for front slides. Probably 9 outta 11 races were on the 70 series that year and I have never raced on anything but a 70 since. My ZX636 came with teh 65 size OEM but I converted to 70 with the very first set....